This invention relates generally to communication or signalling systems for fuel-handling facilities, and more particularly to systems of this type which are adapted to monitor a number of different parameters relating to transfer (as of petroleum) from storage tanks of a stationary facility, to one or more vehicles.
Conventional monitoring systems for sensing the various functions that are associated with fuel or petroleum-carrying vehicles heretofore did not involve multiple waveforms, and also usually employed direct-contact sockets and plugs that use cooperable spring fingers or contacts which are mated with one another when the connector is placed in use. Such arrangements presented a number of problems from both the reliability standpoint and the safety standpoint. Normally the spring contacts in such connectors are plated with a non-corroding metal such as silver or gold, in order to have a good connection between the parts after prolonged use, especially for unfavorable environments characterized by dampness, excessive heat or cold or in corrosive surroundings such as areas exposed to salt spray or other reactants like smoke, soot, sulphur and the like; but even so, failures occurred due to the scraping action of the connection, deformation of the springs, etc.
In addition, where conventional contacts are employed there always exists the danger of sparks arising from the make-and-break nature of the joint. If gasoline or other volatile liquid such as liquefied natural gas is being transferred, such sparks can represent a distinct and very serious hazard.
It is virtually impossible to prevent the contact areas of such connectors from gradually deteriorating with use, due to the abrasion of the plated material, or the physical damage occurring at the spring part itself. Even where silver is employed, tarnishing occurs after a period of time elapses, diminishing the integrity of the connector.
Where connectors of the push-on type are involved, damage is likely to occur if care is not exercised by the operator in installing or removing the one part of the connector. Such devices are often quite susceptible to damage from carelessness, as well as where excessive strain is put on a wire cable while the connector plug is still in place. Also, the possibility always exists that the vehicle might be driven off inadvertently with the connector plug still in operative position, giving rise to permanent damage of the unit. Repair or replacement of such connectors is both timeconsuming and costly, and represents an unnecessary expense, especially if such replacement necessitates a degree of down time for the particular vehicle being serviced. Prior signalling systems in many instances had limitations as to the number and type of indications which could be given, and reliability was considered inadequate when taking into account the large losses that could be incurred as a consequence of equipment or operator error.